In a cellular system, a positioning technique for identifying the position of a terminal using a signal from a plurality of GPS (Global Positioning System) satellites or a plurality of base stations has been used. This technique can identify the position of a terminal with an accuracy of about 10 to 100 m.
However, in an indoor environment, it is difficult to receive a signal from GPS satellites or base stations needed for position identification, preventing highly accurate identification of the terminal position.
As a technique for identifying the position of a terminal used in an indoor environment, there are known positioning techniques such as one using a signal of a wireless LAN (Local Area Network) installed by and used at companies, shops or the like, one using a Bluetooth or RFID (Radio Frequency Identification) system.
In order to perform accurate positioning using a wireless LAN, three or more wireless LAN base stations need to be seen by a positioning target terminal. However, in the wireless LAN, where base stations are not installed under the design of providers unlike the case of a cellular system but are often installed at non-responsive or randomly selected locations, there is no guarantee that the positioning target terminal can see three or more base stations. In a positioning system using a weak radio wave, such as a Bluetooth or RFID system, it is possible to achieve pinpoint positioning while it is necessary to install a large number of communication modules conforming to Bluetooth or RFID to walls and a ceiling, increasing installation cost.
It can be seen, from such a background, it is not practical to install a positioning infrastructure that utilizes a Bluetooth or RFID system only for the positioning operation and, currently, a positioning technique capable of utilizing an infrastructure installed for purposes other than the positioning is required.